Biomedical subjects

C Hinojosa

Publications and source records attributed to C Hinojosa.

6 recordsLinked to original sources

PubMed1986

Plasma vasopressin concentration in high sodium renal hypertension.

One-kidney, figure-8 renal wrapped and sham-operated rats maintained on high sodium intake were studied to determine plasma concentrations of vasopressin during the onset of hypertension. Animals were chronically prepared with femoral artery and vein catheters. Arterial blood samples were taken from conscious rats before and 3 days after renal wrap or sham operation while donor blood was simultaneously infused intravenously. Three days after surgery, arterial pressure, plasma osmolality and plasma vasopressin concentration increased significantly in the renal wrapped animals and remained unchanged in the sham-operated rats. Ganglionic blockade with hexamethonium and atropine produced equivalent decreases in arterial pressure and increases in plasma vasopressin concentration in the two groups of rats. Subsequent administration of the V1 vasopressin antagonist, d(CH2)5Tyr(Me)AVP, caused a significantly greater fall in arterial pressure in the hypertensive rats. These results provide further evidence for a contribution of vasopressin to sodium-dependent hypertension.

Animals↗

PubMed1986

Hemodynamic changes during onset of high-sodium one-kidney figure-8 renal hypertension.

The hemodynamic changes associated with the onset of one-kidney, figure-8, renal-wrap hypertension were monitored in rats fed a high-sodium diet. In addition, the hemodynamic contributions of the sympathetic nervous system (SNS) and arginine vasopressin (AVP) were assessed during the 1st week of hypertension. Renal wrapping caused mean arterial pressure (MAP) to increase significantly from 108 +/- 4 to 140 +/- 4 mmHg on day 5 after renal surgery. The hypertension was associated with a significant bradycardia and no significant change in cardiac output (CO), as measured with an electromagnetic flow probe. Total peripheral resistance (TPR) was significantly elevated to 140% above control value on day 5 after renal surgery. Ganglionic blockade caused similar decreases in MAP and TPR in normotensive and hypertensive animals. Sympathetic blockade after pretreatment with a specific vascular antagonist of AVP, [1-beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(O-methyl)tyrosine]Arg8-vasopressin ([d(CH2)5Tyr(Me)]AVP), caused a greater depressor response in the renal-wrapped animals as compared with the effect of ganglionic blockade alone in these animals. The effect of [d(CH2)5Tyr(Me)]AVP alone on the hemodynamics was not different between the two groups of rats. After ganglionic blockade pretreatment, [d(CH2)5Tyr(Me)]AVP caused a significant decrease in MAP and TPR in the renal-wrapped animals. In addition, the difference in MAP and TPR between the two groups of rats was eliminated after combined blockade of AVP and the SNS. The results of this study indicated that the onset of hypertension was a result of an activation of neurohumoral mechanisms to increase TPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Development of high sodium renal hypertension during chronic blockade of the vascular effects of vasopressin.

Studies in sodium-dependent models of hypertension have shown that arginine-vasopressin (AVP) plays an important role in the maintenance of blood pressure, predominantly through its vasoconstrictor action. In addition to AVP, the sympathetic nervous system (SNS) also acts to maintain blood pressure in high sodium one-kidney, figure-8 renal wrap hypertension. The purpose of this study was to determine if chronic blockade of vascular AVP (V1) receptors affected the induction of high sodium renal hypertension and the contribution of the SNS to the maintenance of blood pressure. Rats receiving chronic s.c. administration of a V1 antagonist, d(CH2)5Tyr(Me)AVP, or vehicle were subjected to renal wrapping or sham surgery, V1 receptor blockade was confirmed periodically by an 80 +/- 3% reduction of the pressor response to a bolus injection of 10 mU/kg of AVP. d(CH2)5Tyr(Me)AVP did not affect the development of hypertension or the associated changes in plasma sodium, potassium, osmolality and hematocrit. In renal-wrapped rats, ganglionic blockade caused a greater fall in blood pressure in animals treated with d(CH2)5Tyr(Me)AVP than in vehicle-treated animals. However, this apparent increase in SNS function was not responsible for the hypertension in d(CH2)5Tyr(Me)AVP-treated, renal-wrapped rats, inasmuch as ganglionic blockade lowered blood pressure a similar amount in normotensive d(CH2)5Tyr(Me)AVP-treated, sham-operated rats and blood pressure remained elevated after combined blockade of the SNS, AVP and the renin-angiotensin systems. These results indicated that chronic blockade of V1 receptors did not alter the induction of high sodium renal hypertension and the mechanism of the elevated blood pressure was not through an activation of the SNS or other neurohumoral mechanisms.

Animals↗

PubMed1985

Neurohumoral mechanisms of sodium-dependent hypertension.

The contribution of neurohumoral factors to arterial pressure has been studied in several models of sodium-dependent hypertension including the deoxycorticosterone-saline, Dahl salt-sensitive rats, and reduced renal mass-saline. Observations from these animals have largely pointed to the sympathetic nervous system and arginine vasopressin (AVP) as the critical factors responsible for mediating the increased arterial pressure. Our work has indicated that the one-kidney, figure-8 renal wrap model of experimental hypertension is also sodium dependent. In these rats, prior sodium depletion prevented the development of hypertension whereas high sodium intake exacerbated the increase in arterial pressure. An activation of the sympathetic nervous system and increased AVP activity appeared to be responsible for the hypertension in rats maintained on normal and high sodium intake. Stimulation of the AVP and sympathetic nervous systems in sodium-dependent hypertension may be associated with a suppression of cardiovascular gamma-aminobutyric acid (GABA)-ergic function in the central nervous system. The inhibitory neurotransmitter, GABA, and an inhibitor of GABA uptake, nipecotic acid, lowered arterial pressure in a sodium-stimulated model of hypertension.

Animals↗

PubMedDate not supplied

Biomedical imaging modalities: a tutorial.

The introduction of advanced imaging technologies has improved significantly the quality of medical care available to patients. Non-invasive imaging modalities allow a physician to make increasingly accurate diagnoses and render precise and measured modes of treatment. Current uses of imaging technologies include laboratory medicine, surgery, radiation therapy, nuclear medicine, and diagnostic radiology. This paper provides an overview of most of the popular imaging modalities currently in clinical use. It is hoped that a general understanding of the modality from which an image is derived will help researchers in the subsequent analysis of the image data.

Angiography, Digital Subtraction↗

PubMedDate not supplied

Contribution of vasopressin and the sympathetic nervous system in the early phase of high sodium one-kidney renal hypertension.

This study assessed the contributions of the sympathetic nervous system and arginine vasopressin to the onset of one-kidney, one-wrap (1K1W) renal hypertension in rats fed a high sodium diet. Two weeks before renal wrap or sham wrap, rats were given a high sodium diet and water ad libitum. At 3 days postwrap, resting mean arterial pressure (MAP) was significantly greater in renal-wrapped rats. The contributions of the sympathetic nervous system and vasopressin to blood pressure (BP) were assessed by ganglionic blockade and vascular vasopressin receptor antagonism, respectively. Depressor responses to ganglionic blockade were significantly greater in the normotensive rats as compared to the hypertensive rats. Administration of vasopressin antagonist caused a significant fall in pressure only in wrapped rats. In addition, enhanced pressor responses to bolus injections of vasopressin were observed in hypertensive rats. These results indicate that during this phase of the hypertension there is an activation of the vasopressin pressor system without an increase in neurogenic function. Equalization of arterial pressure occurred only when both systems were blocked, regardless of the order of blockade, which indicated that the sympathetic nervous system and vasopressin interact to maintain the hypertension. Comparison of depressor responses to the blocking agents revealed that the interaction is compensatory in nature since the contributions of the sympathetic nervous system and vasopressin to the maintenance of arterial pressure were greater when the other system was blocked.

Angiotensin II↗